Manufacturing method of ceramic electronic components and its manufacturing equipment

ABSTRACT

In the step of cladding by applying a pressing force to a ceramic stack body, while a frame being punched into a stack body and kept therein, the stack body is pressed by a pressing force applying member located inside of the frame. According to this method, no deformations are created in the direction parallel to the surface of the stack. Therefore, such a problem as the deformation of a conductive layer due to stress in not caused, resulting in a stack body with an excellent densified structure and, when resulting stack bodies are sintered, ceramic electronic components formed of them are free of defective connections, structural defects and electrical performance failures with an excellent yield rate. In addition, by heating a stack body at applying a pressing force thereto, the densified stack body is formed under a reduced pressure. Furthermore, by having an elastic body provided to the pressing force applying member, a stack body is pressed uniformly. And, by reducing the atmospheric pressure of a stack body at applying a pressing force thereto, gasses inside of the stack body are readily exhausted to allow the pressing period of time to be reduced.

TECHNICAL FIELD

[0001] The present invention relates to a manufacturing method ofceramic electronic components such as a multilayer ceramic capacitor andthe like and manufacturing equipment thereof.

BACKGROUND ART

[0002] Many methods for manufacturing ceramic electronic components havebeen known and a description is made here on a typical manufacturingmethod of multilayer ceramic capacitors.

[0003] First, a powder of such dielectric materials as barium titanateand the like is added with an organic binder, plasticizer, solvent andthe like and the resulting mixture is kneaded and made like slurry.Then, the slurry is coated according to a doctor blade method and thelike and dried to produce a ceramic green sheet. Next, a conductivepaste mainly composed of a metal is printed on the ceramic green sheetby a screen printing method and the like and dried to form a conductivelayer, thereby allowing a sheet for active layer to be prepared. Asidefrom above, a sheet for cover layer composed only of a ceramic greensheet, which has no conductive layer formed thereon, is prepared.

[0004] As FIG. 12 shows, according to a prior art stacking process ofmultilayer ceramic capacitors, adhesive layer 102 is disposed onsupporting plate 101 and a plurality of sheets for cover layer arestacked thereon. Further, on top of that, a sheet for active layer issuperimposed, thus putting together a ceramic green sheet and aconductive layer to form a stack structure. The step of superimposing asheet for active layer is repeated by a predetermined number of timesand further a plurality of sheets for cover layer are again stacked ontop of the plurality of sheets for active layer to realize stack body103. When the sheets for active layer are stacked on top of each other,the stacking is performed in such a manner that a plurality ofrectangular patterns of respective conductive layers, each acting as aninternal electrode, are staggered alternately from layer to layer by apredetermined distance in the length direction of the rectangularpattern.

[0005] In the step of forming a high-density structure by pressing, apressing force is applied to stack body 103 to have respective ceramicgreen sheets and conductive layers pressed against one another to form aone-piece structure. In the prior art step of forming a high-densitystructure by pressing, uniaxial press with flat lower die 111 and flatupper die 112 arranged in parallel with each other is used. Stack body103 as composed on supporting plate 101 via adhesive layer 102 isdisposed on lower die 111 and applied with a pressing force via upperdie 112 to form a high-density structure of stack body 103.

[0006] Next, the high-density structure of stack body 103 is cut topieces, each having a desired configuration, and separated from adhesivelayer 102 on supporting plate 101, to produce green chips. The greenchips are sintered and external electrodes are provided on eachrespective chip to complete a multilayer ceramic capacitor.

[0007] The aforementioned step of forming a high-density structure bypressing is a very important step to prevent a failure due to structuraldefects such as delamination and the like from occurring. When theextent of adhesive joining between respective ceramic green sheets andconductive layers is insufficient, it is likely to cause a failure dueto structural defects. Therefore, in order to establish the densifyingcondition to a sufficient extent, it is necessary for stack body 103 tobe applied with a pressing force uniformly and sufficiently, therebyallowing respective ceramic green sheets to be deformed in the thicknessdirection thereof and to be pressed against each other to realize anexcellent densifying condition.

[0008] However, when a ceramic green sheet is applied with a pressingforce or exposed to a temperature and a pressure needed for densifying,the ceramic green sheet is deformed not only in the thickness directionthereof but also in the direction parallel to the surface thereof. Thismeans that the periphery of stack body 103 tends to expand outwards,thereby causing a distortion in the shape of the conductive layer. As aresult, when stack body 103 is cut into pieces, a failure due todisconnection and a failure due to poor characteristics are caused.These problems are likely to be multiplied as the step-wise differencein level due to missing of a conductive layer is increased becauseincreasing numbers of the conductive layers are involved and/or thethickness of ceramic green sheet is small, thereby making the ratio ofthe thickness of conductive layers occupying in the thickness of stackbody 103 more significant.

[0009] Therefore, various proposals have been made with respect a methodfor preventing the deformation of a stack body from occurring when apressing force is applied thereto. For example, in the Japanese PatentApplication Unexamined Publication Nos. H5-175072 and 2001-23844, a fewdisclosures on the method are made as follows:

[0010] A) A method for forming a high-density structure by firstapplying a pressing force to the periphery on the surface of a stackbody by means of a peripheral section die and then applying a pressingforce to the inner part below the surface of the stack body by means ofa central section die.

[0011] B) A method for applying a higher pressing force to a stack bodyby means of a peripheral section die than the pressing force applied tothe stack body by means of a central section die.

[0012] C) A method for applying a pressing force to a stack body placedin an elastic framework by means of uniaxial rubber press.

[0013] Even according to the A and B methods, however, when thestep-wise difference in level due to missing of a conductive layer islarge, a plastic deformation of a ceramic green sheet takes place notonly in the thickness direction but also in the direction parallel tothe surface of the ceramic green sheet. As a result, the stack bodyexpands at the outer periphery thereof to cause a distortion in theshape of the conductive layer.

[0014] Even according to the C method, it is necessary for thedimensions of the stack body to match the inner dimensions of theelastic framework with a high degree of precision and even a littledifference in the dimensions does not allow the deformation of the stackbody to be prevented from occurring.

SUMMARY OF THE INVENTION

[0015] A manufacturing method of ceramic electronic components accordingto the present invention comprises the step of applying a pressing forceto a stack body formed by stacking ceramic green sheets and conductivelayers on top of each other alternately to form a one-piece high-densitystructure of ceramic green sheets and conductive layers, in which aframe is installed to be held inside the stack body and a pressing forceis applied to a pressing force applying member located inside of theframe. Manufacturing equipment of ceramic electronic componentsaccording to the present invention comprises a lower die, a pressingforce applying member and a frame provided to surround the outerperiphery of the pressing force applying member for applying a pressingforce to a stack body formed by stacking ceramic green sheets andconductive layers on top of each other alternately, in which the tip ofthe frame is shaped like a blade.

BRIEF DESCRIPTION OF DRAWINGS

[0016]FIG. 1 is a cross-sectional view for describing the step ofapplying a pressing force to a stack body to form a high-densitystructure in exemplary embodiment 1 of the present invention.

[0017]FIG. 2 is another cross-sectional view for describing the step ofapplying a pressing force to a stack body to form a high-densitystructure in exemplary embodiment 1 of the present invention.

[0018]FIG. 3 is still another cross-sectional view for describing thestep of applying a pressing force to a stack body to form a high-densitystructure in exemplary embodiment 1 of the present invention.

[0019]FIG. 4 is a cross-sectional view of manufacturing equipment ofceramic electronic components, used in the step of applying a pressingforce to a stack body to form a high-density structure in exemplaryembodiment 1 of the present invention.

[0020]FIG. 5 is a cross-sectional view of a stack body in exemplaryembodiment 1 of the present invention.

[0021]FIG. 6 is a cross-sectional view of manufacturing equipment ofceramic electronic components, used in the step of applying a pressingforce to a stack body to form a high-density structure in exemplaryembodiment 2 of the present invention.

[0022]FIG. 7 is a cross-sectional view of manufacturing equipment ofceramic electronic components, used in the step of applying a pressingforce to a stack body to form a high-density structure in exemplaryembodiment 3 of the present invention.

[0023]FIG. 8 is a cross-sectional view for describing the step ofapplying a pressing force to a stack body to form a high-densitystructure in exemplary embodiment 3 of the present invention.

[0024]FIG. 9 is another cross-sectional view for describing the step ofapplying a pressing force to a stack body to form a high-densitystructure in exemplary embodiment 3 of the present invention.

[0025]FIG. 10 is still another cross-sectional view for describing thestep of applying a pressing force to a stack body to form a high-densitystructure in exemplary embodiment 3 of the present invention.

[0026]FIG. 11 is still another cross-sectional view for describing thestep of applying a pressing force to a stack body to form a high-densitystructure in exemplary embodiment 3 of the present invention.

[0027]FIG. 12 is a cross-sectional view for describing the step ofapplying a pressing force to a stack body to form a high-densitystructure according to a prior art technology.

BEST MODE FOR CARRYING OUT THE INVENTION

[0028] Next, a description is given to various exemplary embodiments ofthe present invention with reference to drawings. With respect to adescription made on the objects structured in a manner similar to oneanother, the same reference symbols are used in common.

Exemplary Embodiment 1

[0029] A description is made on exemplary embodiment 1 with reference toFIG. 1 through FIG. 5.

[0030] First, ceramic green sheet 3 composed of a ceramic powder, whichis mainly formed of barium titanate, and an organic binder is formed ona base film to prepare a first sheet. Meanwhile, a second sheet isprepared by having conductive layer 4 deposited on ceramic green sheet3. This process is performed according to a screen printing method bythe use of a metallic paste mainly composed of nickel to form conductivelayer 4 on ceramic green sheet 3 of the first sheet in a desired patternwith a drying step followed thereafter. At this time, the thickness ofceramic green sheet 3 is made about 10 μm and the thickness ofconductive layer 4 is made about 2.5 μm.

[0031] Next, a description is given to a stacking process. As FIG. 5shows, adhesive sheet 2 is first formed on supporting plate 1. Adhesivesheet 2 plays an important role in making supporting plate 1 integralwith stack body 5 and has adhesion to both stack body 5 and supportingplate 1. The adhesion is strong enough to prevent stack body 5 andsupporting plate 1 from coming off from each other. However, when theintegral structure of stack body 5 and supporting plate 1 is cut intopieces, the composing elements of each respective piece of above areneeded to be separated from each other. Therefore, the adhesion betweenstack body 5 and supporting plate 1 is arranged to disappear when heatedto temperatures higher than a predetermined temperature.

[0032] Then, after the first sheet is transfer printed by bonding on topof adhesive sheet 2 on supporting plate 1 by an application of heat andpressure via the base film, the base film is eliminated by peeling off.This process is repeated to have 20 sheets of the first sheet stacked ontop of each other, resulting in a cover layer.

[0033] Subsequently, after the second sheet is transfer printed bybonding on top of the cover layer by placing the second sheet on thecover layer in such a manner as the side of conductive layer 4 touchesthe cover layer and applying heat and pressure via the base film, thebase film is eliminated by peeling off. This process of transferprinting the second sheet by bonding is repeated 150 times.

[0034] Additionally, 20 sheets of the first sheet are stacked on top ofeach other to form a cover layer on the stacked second sheets, thusobtaining stack body 5 as shown in FIG. 5.

[0035] Next, a description is given to the manufacturing equipment asshown in FIG. 4. Frame 12 of the manufacturing equipment is provided soas to surround the outer periphery of pressing force applying member 13with almost no gaps left therebetween. In order for frame 12 to have thefunction of cutting stack body 5, the surface of frame 12 at the side ofpressing force applying member 13 is aligned in parallel to the sidesurface of pressing force applying member 13 and the tip of frame 12 isshaped like a sharp blade which is angled outwardly. Heaters 14 and areburied in lower die 11 and pressing force applying member 13,respectively, for heating an object to be pressed. In order to securethe object to be pressed, lower die 11 has a provision of fixing theobject to be pressed by suction.

[0036] Next, a description is given to the step of forming ahigh-density structure by pressing with reference to FIG. 1 through FIG.3.

[0037] As FIG. 1 shows, stack body 5 fixed on supporting plate 1 bymeans of adhesive sheet 2 is disposed on lower die 11 of themanufacturing equipment at a predetermined position. And, on the uppersurface of stack body 5 is disposed polyethyleneterephthalate film 6(referred to as “film”, hereafter) of 35 μm thick.

[0038] Then, as FIG. 2 shows, frame 12 is moved down by hydraulicpressure and punched into stack body 5, and makes a stop when the tip offrame 12 touches adhesive sheet 2. After that, pressing force applyingmember 13 is moved down by hydraulic pressure and presses stack body 5inside of frame 12 as FIG. 3 shows. At this time, the temperatures oflower die 11 and pressing force applying member 13 are kept at 80° C. byheaters 14 and 15, respectively. Stack body 5 is pressed for 60 secondsunder the pressure of 60 MPa/cm².

[0039] Subsequently, the hydraulic pressure is reduced to 1 MPa/cm²while pressing force applying member 13 is making a stop after movingdown. While stack body 5 being held, frame 12 is moved up by hydraulicpressure to have frame 12 separated from stack body 5. Then, pressingforce applying member 13 is moved up by hydraulic pressure to havepressing force applying member 13 separated from stack body 5.

[0040] Next, stack body 5 formed into a high-density structure bypressing is removed from lower die 11 of the manufacturing equipmenttogether with supporting plate 1 and adhesive sheet 2, and stack body 5is cut to the required dimensions. Afterwards, stack body 5 cut aparttogether with supporting plate 1 and adhesive sheet 2 is heated to 150°C. to be separated from adhesive sheet 2, thereby producing many piecesof green chips. After subjecting the green chips to a binder eliminatingtreatment in nitrogen gas, the green chips are sintered in a mixedatmosphere of nitrogen and hydrogen gases, in which nickel is preventedfrom oxidation, with the temperatures thereof increased to 1300° C.,thereby obtaining sintered bodies of the chips.

[0041] Each of the sintered bodies is treated with chamfering to havethe inner electrode exposed to both end surfaces thereof. After anelectrode paste mainly composed of copper is applied to both endsurfaces and also to side surfaces of each respective sintered body, thesintered bodies are exposed in a nitrogen atmosphere at 800° C. to formelectrodes. External electrodes composed of nickel are formed on theelectrodes by applying nickel plating thereto and solder are formed onnickel by applying solder plating thereto, thereby producing multilayerceramic capacitors in exemplary embodiment 1 of the present invention.

[0042] By conducting an inspection of the internal structure of therespective multilayer ceramic capacitors produced in exemplaryembodiment 1 through a microscopic observation of cross-sections of thecapacitors, any failures due to structural defects such as adisconnection defect caused by displacement of conductive layers,interlayer stripping, delamination and the like are not observed at all.Electrical characteristics of the multilayer ceramic capacitors are alsoexcellent.

[0043] In the step of forming a high-density structure by pressing stackbody 5 according to a manufacturing method of multilayer ceramiccapacitors in exemplary embodiment 1 of the present invention, apressing force is applied to stack body 5 through pressing forceapplying member 13 located inside of frame 12 while frame 12 beingpunched into stack body 5. Accordingly, since stack body 5 is appliedwith a pressing force while frame 12 is holding securely stack body 5 insuch a manner that no gaps are created between frame 12 and theperipheral side surfaces of stack body 5, no deformations of stack body5 in the directions parallel to the surface thereof are created, therebyeliminating the possibility of causing deformations of conductive layer4 due to a strain imposed thereto and allowing stack bodies with anexcellent cladding structure to be realized. As a result, when the stackbodies are fired to produce sintered bodies, ceramic electroniccomponents produced by the use of such sintered bodies exhibit nofailures due to disconnection, structural defects and defectiveelectrical characteristics and achieve a good yield rate.

[0044] Since heaters 14 and 15 are employed in exemplary embodiment 1 toapply a pressing force to stack body 5 while heat being applied thereto,stack body 5 is softened due to the heat application and, even when apressing force is small in comparison with the case where a pressingforce is applied at ordinary temperatures, a stack body with asufficiently excellent cladding condition is allowed to be realized.Since the conditions for realizing a cladding structure with a pressingforce application can be set up by both factors of temperatures and apressing force, there is a wide range of freedom to adopt appropriateconditions for realizing a cladding structure by pressing in accordancewith the properties of ceramic green sheets that constitute a stackbody.

[0045] Further, a pressing force is applied to stack body 5 via film 6disposed on the upper surface thereof, thereby preventing the pressureapplication surface of pressing force applying member 13 from stickingto stack body 5 to facilitate the separation from each other. Inaddition, the adhesion of dirt and dust to stack body 5 is prevented.

[0046] The manufacturing equipment used in exemplary embodiment 1employs frame 12 that surrounds the outer periphery of pressure applyingmember 13 and the tip of frame 12 is shaped like a blade. By the use ofthe manufacturing equipment thus structured, it is made possible for themanufacturing method in exemplary embodiment 1 of the present inventionto be put into practice, featuring that a pressing force is applied tostack body 5 via pressing force applying member 13 while frame 12 beingpressed into stack body 5 and held securely therein.

[0047] Also, the manufacturing equipment used in exemplary embodiment 1allows pressing force applying member 13 and frame 12 to moveindependently, thereby making it possible for frame 12 to adjustappropriately the extent and force of pressing thereof into stack body 5and for pressing force applying member 13 to adjust the pressing forceand the like in accordance with the thickness and properties of theobject to be pressed, i.e., stack body 5.

[0048] Furthermore, since frame 12 is installed in such a manner that nogaps are left between frame 12 and pressing force applying member 13,there is no possibility for stack body 5 to get into the gaps betweenframe 12 and pressing force member 13, thereby eliminating the cause ofdeforming stack body 5 in shape at the time of applying a pressing forceto stack body 5 via pressing force applying member 13.

[0049] The tip of frame 12 is shaped like a blade in such a manner thatthe inner surface of frame 12 at the side of pressing force applyingmember 13 is aligned in parallel to the side surface of pressing forceapplying member 13. Therefore, when frame 12 is pressed into stack body5, an extra force is not imposed to stack body 5 located at the innerside of frame 12 in the direction parallel to the surface of stack body5, thereby preventing stack body 5 from being lifted and/or deformed.

[0050] The advantages as described in above are applicable to the casewhere ceramic green sheets are thin and even the case where the numberof ceramic green sheets and the number of conductive layers aremultiplied.

Exemplary Embodiment 2

[0051]FIG. 6 is a cross-sectional view of the manufacturing equipment ofceramic electronic components employed in the step of forming ahigh-density structure by pressing in exemplary embodiment 2 of thepresent invention.

[0052] What exemplary embodiment 2 differs from exemplary embodiment 1is in the structure of the manufacturing equipment employed. As FIG. 6shows, the manufacturing equipment in exemplary embodiment 2 of thepresent invention has the pressure application surface on the end partof pressing force applying member 23 composed of elastic body 26 toapply a pressing force uniformly to an object to be pressed. Ahigh-temperature-resistant rubber material is employed as elastic body26. Alternatively, a flat plate composed of a rigid body via a springsupport can be used or a piston-type structure with a gas enclosed canbe employed. Except for the foregoing, the manufacturing equipment inthe present exemplary embodiment is the same as the one of FIG. 4 usedin exemplary embodiment 1.

[0053] Next, a description is given to a manufacturing method of ceramicelectronic components in exemplary embodiment 2 of the present inventionin accordance with the steps constituting the manufacturing method.

[0054] First, stack body 5 is prepared in the same manner as inexemplary embodiment 1.

[0055] With respect to the step of forming a high-density structure byapplying a pressing force to stack body 5, the drawing for describingthe step is omitted since the ascending/descending movement of frame 22and pressing force applying member 23 at the time of forming ahigh-density structure by applying a pressing force to stack body 5 ismade similar to the one in exemplary embodiment 1. And, the step ofdisposing stack body 5 on lower die 21 at a predetermined positionthereof and also disposing a polyethyleneterephthalate film on the uppersurface of stack body 5 as FIG. 6 shows is also similar to the one inexemplary embodiment 1.

[0056] Then, frame 22 is moved down by hydraulic pressure and pressedinto stack body 5. The movement of frame 22 comes to a stop when the tipthereof touches adhesive sheet 2. Thereafter, pressing force applyingmember 23 of the manufacturing equipment is moved down by hydraulicpressure to press stack body 5 inside of frame 22. At this time, heaters24 and 25 maintain the temperatures of lower die 21 and pressing forceapplying member 23 at 80° C. and pressing force applying member 23presses stack body 5 for 60 seconds with a pressing force of 30 MPa/cm².

[0057] Subsequently, the hydraulic pressure is reduced to 1 MPa/cm²while pressing force applying member 23 is making a stop after movingdown. While stack body 5 being held, frame 22 is moved up by hydraulicpressure to have frame 22 separated from stack body 5. Then, pressingforce applying member 23 is moved up by hydraulic pressure to havepressing force applying member 23 separated from stack body 5. Next,stack body 5 formed into a high-density structure by pressing is removedfrom lower die 21 together with supporting plate 1 and adhesive sheet 2.

[0058] In the same way as in exemplary embodiment 1, stack body 5 is cutapart into pieces of green chips. The green chips are sintered, each ofwhich is then provided with external electrodes, thus producingmultilayer ceramic capacitors in exemplary embodiment 2 of the presentinvention.

[0059] By conducting an inspection of the internal structure of themultilayer ceramic capacitors produced in exemplary embodiment 2 througha microscopic observation of cross-section of the capacitors, anyfailures due to structural defects such as a disconnection defect causedby displacement of conductive layers, delamination and the like are notobserved at all. Electrical characteristics of the multilayer ceramiccapacitors are also excellent.

[0060] The manufacturing equipment in exemplary embodiment 2 of thepresent invention has the pressure application surface on the end partof pressing force applying member 23 provided with elastic body 26.Accordingly, the adverse effects caused by irregularities on the surfaceof an object to be pressed, i.e., stack body 5 due to the existence ofconductive layer 4 are absorbed by elastic body 26, thereby allowingstack body 5 to be applied with a pressing force uniformly. The pressingforce applied to stack body 5 in exemplary embodiment 2 is small inmagnitude when compared with exemplary embodiment 1, resulting in anelimination of such a problem as deformations of stack body 5 and yet anexcellent densifying condition of the stack body. As a result, ceramicelectronic component exhibiting no failures due to a disconnectiondefect, structural defects and defective electrical characteristics areproduced with a good yield rate.

Exemplary Embodiment 3

[0061]FIG. 7 is a cross-sectional view of the manufacturing equipment ofceramic electronic components employed in the step of forming ahigh-density structure by pressing in exemplary embodiment 3 of thepresent invention. FIG. 8 through FIG. 11 are cross-sectional views fordescribing the step of forming a high-density structure by applying apressing force to a stack body in exemplary embodiment 3 of the presentinvention.

[0062] What exemplary embodiment 3 differs from exemplary embodiment 1and exemplary embodiment 2 is in the structure of the manufacturingequipment employed and the ascent/descent movement of frame 32 andpressing force applying member 33 at the time of forming a high-densitystructure by pressing. As FIG. 7 shows, the manufacturing equipment ofceramic electronic components in exemplary embodiment 3 is structured toallow the space inside vacuum chamber 37 to be kept under a reducedpressure by exhausting air through air outlet 38. Accordingly, anapplication of a pressing force to a stack body in an atmosphere under areduced pressure facilitates the exhaustion of gasses contained in thestack body, thereby allowing the stack body to realize an excellentdensifying condition. Except for the foregoing, the manufacturingequipment in the present exemplary embodiment is structured in the sameway as the manufacturing equipment of FIG. 6 used in exemplaryembodiment 2.

[0063] Next, a description is given to a manufacturing method of ceramicelectronic components in exemplary embodiment 3 of the present inventionin accordance with the steps constituting the manufacturing method.

[0064] First, stack body 5 as shown in FIG. 3 is prepared in the samemanner as in exemplary embodiment 1.

[0065] Then, as FIG. 8 shows, stack body 5 is disposed on lower die 31at a predetermined position and film 6 is disposed on the upper surfaceof stack body 5. These steps are the same as in exemplary embodiment 1.And, air is exhausted through air outlet 38 provided to vacuum chamber37 to reduce the atmospheric pressure inside vacuum chamber 37 to 13hPa, thereby allowing gasses contained inside of stack body 5 to beexhausted.

[0066] Subsequently, while the atmospheric pressure inside of vacuumchamber 37 being kept at 13 hPa, pressing force applying member 33 ofthe manufacturing equipment is moved down by hydraulic pressure andstops the motion of moving down at a position where a small pressingforce of 1 MPa/cm² is still being applied to stack body 5. Thus, as FIG.9 shows, elastic body 36 attached to the end part of pressing forceapplying member 33 holds and puts stack body 5 in place.

[0067] Next, as FIG. 10 shows, frame 32 is moved down by hydraulicpressure and pressed into stack body 5 and stops the motion of movingdown at a position where the tip of frame 32 touches adhesive sheet 2.Thereafter, the pressing force of pressing force applying member 33 isincreased by hydraulic pressure and stack body 5 inside of frame 32 ispressed as FIG. 11 shows. At this time, heaters 34 and 35 keep thetemperatures of lower die 31 and pressing force applying member 33 at80° C. and stack body 5 is applied with a pressing force of 30 MPa/cm²for 30 seconds.

[0068] Then, while pressing force applying member 33 stopping the motionof moving down, the hydraulic pressure is reduced to 1 MPa/cm². Whilestack body 5 is being held down, frame 32 is moved up by hydraulicpressure to have frame 32 separated from stack body 5. Thereafter,pressing force applying member 33 is moved up by hydraulic pressure tobe separated from stack body 5. And, air is introduced through air inlet39 to return the pressure inside of vacuum chamber 37 to barometricpressure and stack body 5 formed into a high-density structure bypressing is removed together with supporting plate 1 and adhesive sheet2 from lower die 31 of the pressing force applying setup.

[0069] In the same way as in exemplary embodiment 1, stack body 5 is cutapart into pieces of green chips. The green chips are sintered, each ofwhich is then provided with external electrodes, thus producingmultilayer ceramic capacitors in exemplary embodiment 3 of the presentinvention

[0070] By conducting an inspection of the internal structure of themultilayer ceramic capacitors produced in exemplary embodiment 2 througha microscopic observation of cross-section of the capacitors, anyfailures due to structural defects such as a disconnection defect causedby displacement of conductive layers, delamination and the like are notobserved at all. Electrical characteristics of the multilayer ceramiccapacitors are also excellent.

[0071] With respect to a manufacturing method of multilayer ceramiccapacitors in exemplary embodiment 3 of the present invention, anapplication of a pressing force to stack body 5 under a reducedatmospheric pressure facilitates the elimination of gasses containedinside of stack body 5, thereby allowing the adhesion between ceramicgreen sheets to be achieved easily. Although the application of apressing force to stack body 5 is conducted in a short period of time inexemplary embodiment 3 when compared with exemplary embodiment 2, such aproblem as a deformed stack body is not observed and a very excellenthigh-density structure in the stack body is realized. As a result,ceramic electronic components exhibiting no failures due to adisconnection defect, structural defects and defective electricalcharacteristics are produced with a good yield rate.

[0072] In addition, frame 32 is punched into stack body 5 by means ofpressing force applying member 33 with stack body 5 held and put inplace, and then stack body 5 is applied with a pressing force viapressing force applying member 33, thereby allowing stack body 5 to befixed in position by means of pressing force applying member 33 and alsoto be prevented from being lifted or delaminated when the air inside ofvacuum chamber 37 is exhausted to create the state of a reduction inatmospheric pressure. Even when frame 32 is punched into stack body 5,any lifting or deformation in stack body 5 is not caused.

[0073] With respect to a method of stacking layers on top of each otherto produce stack body 5 in exemplary embodiment 1 through exemplaryembodiment 3, a description is given to a method comprising the steps oftransferring by adhesion ceramic green sheet 3 onto adhesive sheet 2 onsupporting plate 1 via a base film by applying heat and pressure andeliminating the base film by peeling off. The present invention isequally effective in the case of forming a high-density structure byapplying a pressing force to a stack body, which is produced accordingto a stacking method different from the aforementioned transfer stackingmethod.

[0074] Although a description is given to preparations of multilayercermamic capacitors in exemplary embodiment 1 through exemplaryembodiment 3, the present invention is equally effective in the case ofproducing a stack body formed by stacking ceramic green sheets andconductive layers on top of each other and used in ceramic electroniccomponents such as multilayer coils, multilayer varistors, multilayerthermisters, ceramic multilayer substrates and the like.

INDUSTRIAL APPLICABILITY

[0075] As described in above, the present invention deals with amanufacturing method of ceramic electronic components, in which theprocess of forming a cladding structure by applying a pressing force toa stack body formed by stacking ceramic green sheets and conductivelayers on top of each other comprises the steps of having a framepunched into the stack body and kept therein and applying a pressingforce the stack body via a pressing force applying member located insideof the frame. According to this method, a pressing force is allowed tobe applied to the stack body held and fixed in position by the frame insuch a way that there are no gaps created at all between the frame andthe peripheral side surfaces of the stack body. Therefore, even when asufficiently strong pressing force is applied to the stack body to forma high-density structure, the stack body can be prevented from beingdeformed in the direction parallel to the surface thereof, therebyrealizing a reduction in disconnection failures and also in performancefailures. After the resulting stack bodies are sintered, ceramicelectronic components free of structural defects and failures inelectrical performance are allowed to be produced with an excellentyield rate by using the sintered bodies.

[0076] The present invention also deals with manufacturing equipmentcomprising a lower die, a pressing force applying member and a frameprovided so as to surround the peripheral side surfaces of the pressingforce applying member for the purpose of pressing an object to bepressed, in which the tip of the frame is shaped like a blade. By theuse of the manufacturing equipment, a manufacturing method of ceramicelectronic components, the method comprising the step of applying apressing force to a stack body via a pressing force applying memberlocated inside of a frame while the frame being punched into the stackbody and kept therein, is made possible.

1. A manufacturing method of ceramic electronic components, comprisingthe steps of; punching a frame into a stack body formed by stackingceramic green sheets and conductive layers on top of each other; andforming a high-density structure by applying a pressing force to saidstack body via a pressing force applying member located inside saidframe.
 2. The manufacturing method of ceramic electronic componentsaccording to claim 1, wherein the step of forming a high-densitystructure by applying a pressing force further comprises the step ofheating said stack body.
 3. The manufacturing method of ceramicelectronic components according to claim 1, further comprising the stepof placing said stack body under a reduced atmospheric pressure.
 4. Themanufacturing method of ceramic electronic components according to claim1, further comprising the step of fixing and keeping said stack body inplace by means of said pressing force applying member.
 5. Themanufacturing method of ceramic electronic components according to claim1, wherein a tip of said frame is shaped like a blade.
 6. Themanufacturing method of ceramic electronic components according to claim1, wherein said frame is provide to surround an outer periphery of saidpressing force applying member with no gaps left therebetween.
 7. Themanufacturing method of ceramic electronic components according to claim1, wherein each respective inner side surface of said frame locatedclose to said pressing force applying member extends to a tip of saidframe in parallel to a side surface of said pressing force applyingmember.
 8. The manufacturing method of ceramic electronic componentsaccording to claim 1, wherein said pressing force applying member andsaid frame are movable independently from each other.
 9. Themanufacturing method of ceramic electronic components according to claim1, wherein an elastic body is provided to said pressing force applyingmember.
 10. Manufacturing equipment of ceramic electronic components,comprising: a lower die and a pressing force applying member to press astack body formed of ceramic green sheets and conductive layers stackedon top of each other; and a frame provided to surround an outerperiphery of said pressing force applying member and to be punched intosaid stack body.
 11. The manufacturing equipment of ceramic electroniccomponents according to claim 10, wherein a heater is provided to atleast any one of said lower die and pressing force applying member. 12.The manufacturing equipment of ceramic electronic components accordingto claim 10, further comprising a chamber at least allowing a stack bodyto be contained therein by sealing so as to have an inside thereofreduced in atmospheric pressure.
 13. The manufacturing equipment ofceramic electronic components according to claim 12, further comprisinga pressure reducing device for reducing an atmospheric pressure insideof said chamber.
 14. The manufacturing equipment of ceramic electroniccomponents according to claim 10, wherein said pressing force applyingmember fixes and puts a stack body in place.
 15. The manufacturingequipment of ceramic electronic components according to claim 10,wherein a tip of said frame is shaped like a blade.
 16. Themanufacturing equipment of ceramic electronic components according toclaim 10, wherein said frame is provided so as to have no gaps leftbetween said frame and said pressing force applying member.
 17. Themanufacturing equipment of ceramic electronic components according toclaim 10, wherein each respective inner side surface of said framelocated close to said pressing force applying member extends to a tip ofsaid frame in parallel to a side surface of said pressing force applyingmember.
 18. The manufacturing equipment of ceramic electronic componentsaccording to claim 10, wherein said pressing force applying member andsaid frame are movable independently from each other.
 19. Themanufacturing equipment of ceramic electronic components according toclaim 10, wherein an elastic body is provided to said pressing forceapplying member.